This answer doesn't address the "feels right" versus "logical" conflict in the question, it simply states your preference. The issue is that when I am you, your mom is mine.
– nmcleanApr 11 '14 at 17:50

Over the years I've converted to the belief that what is important in language and grammar is that the communication is not unintentionally ambiguous, not that it satisfies any formal criterion. Whether you say your mum or my mum, no one is going to be confused by what you mean. So use whichever feels right to you.

Compare to

A: I just spent $5 on the worst cup of coffee ever.

B: If I were you, I'd want my money back.

Seems totally wrong to me to say If I were you, I'd want your money back, but formally it is completely analogous to saying If I were you, I'd apologize to your mum.

On the other hand, I agree with keshlam that it is harder to get confused when you say "your mum" because if B were A and stayed A throughout the sentence (as in the coffee dialog example), who's mother would be "your mum"? There's no "you" left in that situation, so obviously B has popped out of the hypothetical position by that point and "your mum" must still refer to A's mum.

Also, saying "your mum" feels more empathetic and keeps the focus on A's mum rather than discussing how B would treat B's mum, so I would probably say "your mum" even though I would never say "your money".

Back to the coffee dialog, "my mum" could mean either A's mum or B's mum, but in either case the message is the same: If I had said bad things to my mum, I would apologize to my mum. The idea that A should apologize to B's mum is so absurd that the statement If I were you, I'd apologize to my mum is not ambiguous in practice. No one would ever think that B is suggesting A get B's money back for the coffee, right?

With coffee money, there's no simple way of A getting B's money back, of course; but with mothers, it doesn't require much of a stretch to make my obviously refer to the ‘other’ mother: “I think I really put my foot in my mouth with your parents… I should go say sorry to your dad.” — “Nah, dad's laid back, he doesn't care. If I were you, I'd apologise to my mum instead, she's the touchy one.”
– Janus Bahs JacquetApr 13 '14 at 13:34

@JanusBahsJacquet I don't get your point. The OP's question is: after the phrase "If I were you" who is the "me" and "you" that "my" and "your" refer to? I say that for "mums" it is probably best understood that "my" continues to refer the person who said "if I were you" and "your" to the person addressed, and you seem to be saying the same thing as though it is different.
– Old ProApr 15 '14 at 1:29

I was just saying that it's not quite true that the idea that A should apologise to B’s mum is so absurd that the statement is necessarily unambiguous. Given the right context, it could be logical enough to become ambiguous.
– Janus Bahs JacquetApr 15 '14 at 6:42

With "your mum" it is at least clear whose mum is being referred to - A's. In supposing B is A, it's not clear whether we are also supposing "B's mum" now refers to A's. But "your mum" can only refer to A's mum, since supposing B is A doesn't make A anyone else but A.

Really? When B says "your mum" to A who else other than A's mum might he be referring to?
– Neil WApr 12 '14 at 3:36

It could be "your mum" coming from the speaker as he is now, i.e. the listener's mother, or "your mum" coming from the speaker in when "I were you" holds, i.e. coming from the listener, i.e. the speaker's mother.
– einpoklumApr 12 '14 at 6:40

1

@einpoklum: "You" really has no definition within the alternate reality that's just been constructed -- me being you doesn't automatically make you me. :) "You" might not even exist. So we're forced to go back to the real world for a definition.
– cHaoApr 12 '14 at 17:10

Hey, I just call it like I read it, if you need to argue to convince me ex-post-facto that it's not confusing, that doesn't really make your case :-(
– einpoklumApr 12 '14 at 19:34

"My mom" is grammatically correct -- I ... my. As to which one is clearer to the listener, depends on the context. If there were possible ambiguity as to whether your mom or my mom potentially deserved an apology, "your" removes any such ambiguity.

Having had 2 parents with English PhDs, one an English professor, I'm somewhat inured to the value of the grammar police's opinions. I favor clarity over correctness always, and sometimes wrongness over sounding pretentious. The phrase "This is she," for example, has always smacked me as overly grammatical while simultaneously seeming no more technically correct than "This [person, the subject of this sentence] is her [the object, a deitic reference to the person you referred to in your question]."

This is a workaround that works well; unfortunately, it does not answer the question.
– Em1Apr 11 '14 at 9:39

@Em1 Because there isn't really an answer to the question. The question reminds me a little of the famous one about a man standing on the bank of a river. He jumps in. Where was he when he jumped? On the bank? No, that was before he jumped. In the river? No that was after he jumped. In the air? No that was also after he jumped. So where was he? Not every question about use of language has an answer.
– WS2Apr 11 '14 at 10:02

1

Well,this question surely contains more a logical aspect rather than a language's. Consider:If I were you, my actual mum cannot be my mum any more(except we're siblings). So, referring to "my mum" would be incorrect. However, if I were you, your mum becomes my mum, because I am you. So, referring to "my mum" would be correct. – But still, there must be a way to handle that. Probably, differences exist between languages or cultures. So, the question asks for how it is usually handled by English speaker. If there's no answer because, for instance, BE handles it differently than AE then say that.
– Em1Apr 11 '14 at 11:03

2

@Em1 No, it centres around how language is actually used rather than whether it's used as logically as one might like. The key is whether the deictic 'your' is referring to the addressee's mum throughout, or whether it switches with the notional switch of personality. And since personality switch is impossible and therefore illogical anyway, the only way to decide on terminology is arbitrarily.
– Edwin AshworthApr 11 '14 at 15:48

@Em1 When you say 'there must be a way to handle that', remember you are dealing with language, which is an art form. It is not a science like mathematics, or physics which conform to logic and rationality. It is perhaps because we are so used to living in a scientific and technical age that the idea that there is no logical solution to a problem seems foreign to our daily experience. Sometimes with English there is no rational answer where you think there has to be one.
– WS2Apr 11 '14 at 19:25

You (A) have just told me (B) you've said bad things to your mum. Not my mother - your own mother.

So, when I reply to you, I'm talking about your mum (who you have offended), not my own mum (who is not offended). Therefore it's correct to say "your mum" to you, whose mother is offended. Because it's not "my mum" at all, it's yours.

@Mari-LouA Sir I was talking about possible meanings of that sentence. "become person A" its just an imagination. If I have done any mistake then kindly correct me.
– SinghApr 13 '14 at 1:38

@Mari-LouA Sorry ma'am. I haven't seen your profile so by mistake I have written 'sir'. Thanks for correcting me. I would like to say to you that for a minute just look this problem, like it is not from English language but a problem from mathematical reasonings.
– SinghApr 13 '14 at 6:14

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